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In maps__split_kallsyms(), it assumes new kernel map when it finds a
symbol without module after any module and the initial kernel map has
some symbols. Because it expects modules are out of the kernel map so
modules should not have symbols in the kernel map.
For example, the following memory map shows symbols and maps. Any
symbols in the module 1 area will go to the module 1. The main kernel
map starts at 0xffffffffbc200000. But if any symbol has a module
between the symbols in that area, next symbols after 0xffffffffbd008000
will generate new kernel maps like [kernel].1.
kernel address | |
| |
0xffffffffc0000000 |---------------------|
| (symbols) |
| ... | <--- [kernel].N
0xffffffffbc400000 |---------------------|
| (symbols) |
| module 2 | <--- bad?
0xffffffffbc380000 |---------------------|
| ... |
| (symbols) |
| [kernel.kallsyms] | <--- initial map
0xffffffffbc200000 |---------------------|
| |
| |
0xffffffffabcde000 |---------------------|
| (symbols) |
| module 1 |
0xffffffffabcd0000 |---------------------|
This is very fragile when the module has a symbol that falls into the
main kernel map for some reason. My system has a livepatch module with
such symbols. And it created a lot of new kernel maps after those
symbols. But the symbol may have broken addresses and the later symbols
can still be found in the initial kernel map.
Let's check the symbol address in the initial map and use it if found.
Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.